Possible reasons for oil leaking from the automatic transmission:
1. Overflow. Excess transmission fluid can cause it to leak through the breather or other seals.
2. Faulty breather. The breather should clear air from the transmission, but if worn or clogged, it can cause excessive pressure and expel oil.
3. Faulty gaskets or seals. Over time, gaskets and seals can wear or become damaged, causing oil to leak from the connections in the transmission.
4. Bearing wear. Worn bearings can create gaps through which oil can leak.
5. Damaged gearbox housing. The transmission housing may be damaged by impacts, knocks or collisions, causing oil leakage.
6. Faulty oil pump. A faulty oil pump may not generate enough pressure to pump oil through the entire system, resulting in insufficient lubrication and oil leakage.
7. Excessive heat. Excessive heat in the transmission can cause seals and gaskets to expand and lose shape, causing oil leakage.
8. Problems with the cooling system. A faulty radiator or heat exchanger can cause transmission temperatures to rise and oil leaks.
9. Incorrect installation. An improperly installed or tightened transmission can damage seals or gaskets, causing oil leakage.
10. Wear of friction clutches. Worn transmission clutches can release particles that can clog the breather or other components, causing pressure to build up and oil to blow out.